C. van der Meer

Trypanosoma brucei: an evaluation of salicylhydroxamic acid as a trypanocidal drug.

Abstract The chemotherapeutic potential of salicylhydroxamic acid (SHAM) was studied in adult rats infected with a strain of Trypanosoma brucei that kills the rats in about 100 hr. The median lethal dose, administered intraperitoneally in a carboxymethyl-cellulose suspension, is approximately 820 mg/kg body weight for male and 850 mg/kg for female rats. The apparent cause of death is severe depression of the central nervous system. Half-maximal inhibition of O2 uptake by trypanosomes in vitro requires 15 μM SHAM, whereas 100 μM inhibits over 90%. This inhibitory effect on trypanosome respiration was used as a biological assay for the effective SHAM concentration in rat plasma. After administration of a sublethal SHAM dose to rats, the effective plasma SHAM concentration rose rapidly to about 500 μM and then fell to about 10 μM at 4 hr. Nevertheless, this dose did not significantly affect the survival time of rats infected with T. brucei. Even if, by repeated SHAM administration, the plasma SHAM concentration was kept at around 100 μM for more than 4 hr, no therapeutic effect was observed. These results show that O2 uptake is not essential for the survival of trypanosomes in rats and they support the idea that bloodstream trypanosomes have an alternative pathway for glycolysis, allowing energy production in the absence of respiration. The possibility that SHAM or other inhibitors of trypanosome respiration could stilll be trypanocidal if used in conjunction with another inhibitor of glycolysis is discussed.

Isolation and some biochemical properties of a paralysing toxin from the venom of the wasp Microbracon hebetor (Say).

Abstract A toxin with paralysing activity was isolated from crude preparations of Microbracon hebetor (Say) venom by ion exchange chromatography on DEAE-Sephadex A-50, gel chromatography on Sephadex G-100, electrophoresis on polyacrylamide gel and gel chromatography on Sephadex G-75. The active component is very labile. A 28-fold purification was obtained with a recovery of about 2.5% of the original biological activity. The toxin shows one single protein band after disc electrophoresis. The molecular weight was assessed at 61,000 by gel chromatography, and at 62,700 by the sedimentation equilibrium method. The isoelectric point was at pH 6.8. The purified toxin was inactivated by a number of proteolytic enzymes.

Trypanosoma brucei: trypanocidal effect of salicylhydroxamic acid plus glycerol in infected rats.

Abstract Rats inoculated with Trypanosoma brucei brucei EATRO 427 and having a high degree of parasitemia were treated with a series of intra-peritoneal injections of Salicylhydroxamic acid (SHAM) plus glycerol. Permanent cures were obtained with 380 mg/kg SHAM plus 3.8 g/kg glycerol, a dosage regime which was just sublethal. Using a regime with which permanent cure was obtained, the SHAM concentration in the blood plasma remained above 2 mmole/liter for about 20 min, while the glycerol concentration remained above 22 mmole/liter for about 1 hr. The brain concentration of SHAM was close to the plasma concentration. The concentration of glycerol in the brain remained far below the plasma concentration, reaching 6 to 8 mmole/liter between 1 and 2 hr after the beginning of treatment. Treatment with glycerol did not affect the mobility of the trypanosomes nor the survival of infected rats after treatment with suramin.

The Toxicity of Sodium Pentachlorophenolate for Three Species of Decapod Crustaceans and Their Larvae

Pentachlorophenol (PCP) is used extensively as a biocide and has been detected in toxic concentrations in aquatic environments. PCP is a potent uncoupler of oxidative phosphorylation (WEINBACH 1954, 1956) and this effect has been considered to be at least partly responsible for its toxic effects (WEINBACH and NOLAN 1956). Apart from the effect on oxidative phosphorylation stimulation or inhibition of a large number of enzyme systems has been described (KRUEGER et al. 1966, ISHAK et al. 1970, ISHAK 1972, BOSTROM and JOHANSSON 1972). According to HOLMBERG et al. (1972) the effect of subtlethal concentrations of PCP in the eel Anguilla anguilla L. is comparable to an exercise or stress situation. According to GOODNIGHT (1942), MANN (1957) and WEBER (1965) the lethal concentrations of PCP for a number of fishes vary between 0.2 and I ppm. For Anguilla anguilla it must lie somewhat above 0.1 ppm (HOLMBERG et al. 1972) while DAVIS and HOOS (1975) showed that for a number of salmonids the LC50 96 h at 10vC varies from 0.037 to 0.130 ppm. WEINBACH and NOLAN (1956) mention that a concentration of 3 ppm kills a number of water snails. According to MANN (1957) and WEBER (1965) Tubifex sp. can survive at 0.5 ppm. According to GOODNIGHT (1942) insect larvae survive at 5 ppm and according to MANN (1957) at 1.1 to 2.2 ppm. GOODNIGHT (1942) stated that Cambaris virilis Hagen, the amphipod Hyelella knickerbockeri (Bate), Daphnia pulex (de Geer) and Asellus communis Say survived at 5 ppm Na-PCP. MANN (1957) mentions that Cladocerans and Amphipods survive at 0.5 ppm, while WEBER (1965) exposed Daphnia magna to 1.0 ppm and found 30% mortality after 6 h and 100% mortality after 21 h, but no mortality at 0.5 ppm. In the present paper the toxicity of Na-PCP for two marine decapods i.e. Crangon crangon (Linnaeus) and Palaemon elegans (Rathke) and one brackish water decapod i.e. Palaemonetes varians (Leach) has been

The effect of oximes on isolated organs intoxicated with organophosphorus anticholinesterases

Abstract The oxime concentration needed for “complete functional recovery” of the isolated diaphragm treated with organophosphorus anticholinesterases, varies considerably with the inhibitor used. After Soman “aging” of the inhibitor—cholinesterase combination product is completed in about 60 min. With the other anticholinesterases used, “aging” cannot be observed within 4–6 hr. The degree of functional recovery observed can be correlated with the percentage reactivation of the acetylcholinesterase in the diaphragm. The marked variation in the oxime concentration needed to counteract the effect of different anticholinesterases, was confirmed using the isolated rat hind-quarter preparation perfused with blood and using the isolated rat ileum. In contrast to this the dose of atropin needed to counteract various inhibitors in the rat ileum shows very little variation. It is concluded that two factors are important in the oxime treatment of anticholinesterase poisoning, i.e. the effective oxime concentration and the “aging” rate. The relative preponderance of these factors varies with the anticholin-esterase used.

Toxicity of sodium chromate and 3,4-dichloroaniline to crustaceans

Small adult and larval crustaceans are important components of a number of food webs. Therefore, it is important on the one hand to determine the sensitivity of these crustaceans to environmental contaminants and on the other hand to select the most sensitive species as test organisms to help establish the permissible contamination. In brackish water adults as well as larvae of the species Palaemonetes pugio and Uca pugilator have been most frequently investigated. These species can also be studied in sea water. The marine species Carcinus maenas, Crangon septemspinosa and Homarus americanus have also been studied relatively intensively. The present paper describes the toxicity, at different salinities, of Na/sub 2/, CrO/sub 4/, (chromate) and 3,4-dichloroaniline (3,4-DCA) to a number of relatively small adult and larval crustaceans. Chromate was chosen as a model of a heavy metal since, although its toxicity may be relatively low, it may under certain circumstance have considerable environmental effects. Moreover, bichromate has been recommended as a standard in Daphnia tests. 3,4-dichloroaniline was chosen as a model of a chlorinated hydrocarbon, the handling of which does not need special precautions.

Effect of 3-aminobenzamide on antigenic variation of Trypanosoma brucei

African trypanosomes, like Trypanosoma brucei, depend on antigenic variation to evade the immune response of the vertebrate host. An antigenic switch corresponds to the activation of a variable surface glycoprotein (VSG) gene from a large silent repertoire. Most switches require the duplicative transposition of a VSG gene, which involves strand breaks in DNA and subsequent repair. The nuclear enzyme adenosine-diphosphoribosyl transferase (ADPRT), which is dependent on the presence of DNA strand breaks for its activity, might be involved in this process because it has a regulatory role in DNA repair in all eukaryotic cells studied so far. In previous work, the presence of ADPRT activity was demonstrated in T. brucei. Moreover, it was also shown in isolated trypanosomes the ADPRT activity, which is stimulated by the induction of DNA strand breaks, could be blocked by the competitive inhibitor 3-aminobenzamide. Here we report experiments using rats which were infected with small numbers of T. brucei expressing VSG gene 118. After two days, the rats were coupled to a continuous intraperitoneal infusion system administrating 3-aminobenzamide in 0.9% NaCl (81.4 mM) at a rate of 0.65 ml/hr/rat for a period of up to five days. Control rats received only a 0.9% NaCl infusion. At days 1, 3 and 5, 250 microliters blood was obtained from a tail artery. Plasma 3-aminobenzamide was determined using a new high performance liquid chromatography method, developed for these experiments. In most rats the plasma concentrations were maintained between 0.8 and 1.2 mM. The rate of antigenic switching was determined by quantitating the fraction of trypanosomes that had lost their VSG 118 coat, using antibody against VSG 118 and a limiting dilution in mice. The average switching rate found was 2.0 X 10(-6) in controls and 1.3 X 10(-7) in drug-treated rats (15-fold reduction). This suggests that ADPRT is required for completing most antigenic switching events. We discuss the possibility that drug-resistant switching only involves non-duplicative VSG gene activation.

A new public antigen shared by all HLA-A locus products except HLA-A23, -A24, -A32, and -A25 is probably influenced by the amino acid residue at position 79 in the α1 domain

One of the most striking features of HLA gene products is their high degree of polymorphism. The most effort was aimed at the definition of private HLA antigens, and as a result, almost a hundred HLA alleles received official recognition by the WHO Nomenclature Committee. However, thus far little attention has been focused on the definition and the biological relevance of HLA antigenic determinants, shared among various HLA products. Public HLA specificities have been defined by pregnancy sera and by monoclonal antibodies (mAb) (Konoeda et al. 1986, Parham et al. 1986, Spear et al. 1985). An important reason for defining public HLA specificities is the recognition that public specificities represent polymorphic epitopes that can function as alloantigens. This would have important implications for the study of HLA and disease associations and for transplantation studies (Konoeda et al. 1986). Two of the public HLA determinants first described were the Bw4 and Bw6 specificities (Van Rood 1962). Originally, they were identified by pregnancy sera as products of a diallelic system in genetic linkage with the HLA-B-locus-encoded alloantigens. It was shown that these public determinants were spatially distinct from the private determinants of the H L A B locus alleles (Parham 1983). More recently, it became evident that the expression of Bw4 and Bw6 epitopes is not strictly limited to HLA-B locus antigens. The Bw4 epitope appears to be present on HLA-A23, HLA-A24, and HLA-A32 molecules as well, and HLA-Cw3 carries a determinant related to Bw6 (Muller et al. 1982, Kostyu et al. 1980). In the present study, we describe a new public HLAspecificity recognized by a mouse lymphocytotoxic mAb. This mAb, 3Gl l , is of the IgM isotype and recognizes a determinant shared by all HLA-A locus products with the exception of the Bw4-associated HLA-A antigens.

Tryptic peptides from rabbit and bovine albumin enhancing the effect of bradykinin

Abstract Six peptides have been isolated from a tryptic digest of rabbit plasma by ultrafiltration, gel filtration and ion-exchange chromatography; they have been characterized by their isoelectric points, amino acid composition, N-terminal amino acids and biological activities. Two of these peptides potentiated bradykinin, one (peptide A-VI) by a factor of 2 at a concentration of 0.09 mM and the other (peptide A-VII) by a factor of 2 at a concentration of 0.07 mM. Analysis by phenylisothiocyanate degradation as well as by mass spectrometry revealed that the amino acid sequence of peptide A-VI was: Leu-Val-Glu-Ser-Ser-Lys, while that of peptide A-VII was: Thr-Pro-Val-Ser-Glu-Lys. These biologically active peptides were found to originate from the albumin. The amino acid sequence of a biologically inactive peptide (A-VIII) as determined by mass spectrometry was: Ala-(Ile, Leu)-Ser-Ala-Ala-Gln-Glu-Arg. Ten peptides have been isolated from a tryptic digest of bovine albumin. Two of these potentiated bradykinin, one (peptide C-IV) by a factor of 2 at a concentration of 0.07 mM and the other (peptide D-V) by a factor of 2 at a concentration of 0.13 mM. Peptide C-IV had the same sequence as peptide A-VII, while the amino acid sequence of peptide D-V was: Ile-Glu-Thr-Met-Arg. The following peptides have been synthesized by the solid phase method and purified by ion-exchange chromatography: Leu-Val-Glu-Ser-Ser-Lys (peptide A-VI), Val-Glu-Ser-Ser-Lys and Val-Glu-Ser-Lys. The first one potentiated bradykinin by- a factor of 2 at a concentration of 0.11 mM, the second one by a factor of 2 at a concentration of 0.13 mM, while the third one was biologically inactive at a concentration of 1.7 mM. A possible relationship between structure and function of these peptides is discussed.

The pharmacology of KCN as a prophylactic against radiation

Abstract A dose of 100 μg of KCN protects about 80 per cent of mice against a lethal dose of total body irradiation; on lowering the dose the protection decreases rapidly. A protective dose of KCN markedly reduces the oxygen tension in the spleen and bone marrow of these mice. The same dose reduces the total oxygen consumption of the animal to about 25 per cent. The respiration is slowed considerably but the respiratory volume shows little change. The oxygen saturation of the arterial blood is unaltered, the saturation of the venous blood is increased. After an initial fall with about 50 mm Hg the blood pressure rises again but remains about 20 mm below normal. Concurrently with the hypoxia in the spleen and bone marrow the oxygen tension in the brain is augmented considerably. It is concluded that KCN protects against radiation by causing hypoxia in the blood-forming organs. This hypoxia is probably caused by a severe local vasoconstriction due to intense vasomotor stimulation.